The use of gaskets in bell and spigot pipe joints is well known. These gaskets are typically ring-shaped and are stretched around a spigot end of a first pipe. The spigot end is then inserted into a bell end of a second pipe. The pipes can be made from numerous materials, but most commonly are made from concrete or plastic. It is common practice to utilize a surface lubricant to facilitate the jointing of the pipe and gasket.
In a pipe joint that uses a gasket known as a “rolling gasket,” as the spigot end is inserted into the bell end, there is an annular space between an external surface of the spigot and an internal surface of the bell. The gasket has a cross section larger than this clearance. Thus, the gasket rolls along the surfaces of the pipe ends until the first pipe is pushed home. The home position is where an annular end of the first pipe contacts an annular inner shoulder of the second pipe and an annular end of the second pipe contacts an annular outer shoulder of the first pipe.
Some of the known cross sections for rolling gaskets include a circular cross section, a teardrop-shaped cross section, and a D-shaped cross section. The circular gasket is a typical O-ring gasket. O-ring gaskets have been known to “back out” of a pipe joint. This happens when a movement of the pipes and/or forces on the pipes results in the O-ring gasket moving out of the joint area. Teardrop-shaped and D-shaped gaskets were introduced to overcome the disadvantage of the O-ring gasket's tendency to back out; however, these shapes were far enough removed from a circular cross section that is was hard to get these gaskets to roll evenly when inserting the spigot into the bell. A gasket that is difficult to roll can result in rotational misalignment. But, lubrication of the joint requires an additional step during pipe installation, which adds to the cost of the installation.
Accordingly, it is desirable to provide a gasket that rolls evenly when a spigot end of a pipe is inserted into a bell end of a pipe, while at the same time configuring the gasket to inhibit it from “backing out” of a pipe joint. Furthermore, eliminating the need for surface lubricants provides cost savings in time and material.